Our goal is to understand mechanisms by which estrogens affect the brain and cognitive performance. Estrogens have many beneficial effects in the brain; however, the mechanisms by which estrogens mediate these effects are in many ways unknown. We hypothesize that these effects reflect in large part effects on multiple interacting neurotransmitter pathways in specific brain regions. In particular, we hypothesize that loss of ovarian function results in multiple and simultaneous decreases in specific monoaminergic pathways in the brain, and that selective agonists acting at specific estrogen receptors can reverse these effects and restore the neurotransmitter pathways to a physiologically normal state. Over the past decade, Dr. Yao's (co-PI) laboratory has focused on developing technologies to quantify multiple low-molecular weight redox-active compounds (e.g., monoamines, monoamine metabolites, amino acids, markers of oxidative stress, etc...) in biological tissues. This is accomplished using state-of-the-art high-pressure liquid chromatography coupled with a 16-channel Coulometric Multi-Electrode Array System (HPLC-CMEAS) and capillary gas chromatography with a flame-ionization detector (GC-FID). The power of this technology is the ability to assess multiple metabolites from different biochemical pathways simultaneously in the picomol range. Using animal models of both surgical and natural menopause, we will apply this technology to evaluate the effects of 'menopause' and treatment with selective estrogen receptor agonists on multiple neurotransmitter pathways within specific brain regions. Models of menopause will include ovariectomy (a model of surgical menopause), and treatment with 4-vinylcyclohexene diepoxide (VCD; a model of natural menopause). Estrogen treatments will include 17ss-estradiol (E2), G-1 (a selective GPR30 agonist), PPT (a selective ER agonist) and DPN (a selective ERss agonist) administered continuously sc. at 5 g/day for 1 week or six weeks following loss of ovarian function. Tissues from the hippocampus, frontal cortex, and striatum will be dissected and analyzed for levels of monoamines, monoamine metabolites, amino acid neurotransmitters, and choline acetyltransferase (a marker of cholinergic neurons). This study will provide a detailed description of the changes in neurochemically relevant compounds that occur in specific regions of the brain, in two models of menopause, in response to selective hormone treatments. The studies also will be the first to evaluate the effects of a selective GPR30 agonist on these targets and to compare them with the effects of selective ER and ERss agonists. The findings will provide a much clearer understanding of the neurochemical changes associated with different types of menopause and will lead to better strategies for approaching estrogen therapy in women.